Information storing disk, reproduction apparatus, and reproduction method

ABSTRACT

An information storing disk including at least one system stream stored thereon. The at least one system stream includes a silent cell for defining a silent period and an audio cell for defining audio data to be reproduced after the silent period. The silent period is a period to be silent, which is from when one system stream to be reproduced among at least one system stream is determined until reproduction of an audio cell included in the one system stream is started.

This application is a continuation of Ser. No. 09/172,576 filed Oct. 14,1998 now U.S. Pat. No. 6,222,806.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information storing disk for storinga system stream, and an apparatus and a method for reproducing thesystem stream from the information storing disk. In particular, thepresent invention relates to an information storing disk for allowing aplurality of reproduction apparatuses having different levels ofperformance, such as data processing speed, to have the same wait timebefore the reproduction of the system stream starts, and an apparatusand a method for reproducing the system stream from the informationstoring disk.

2. Description of the Related Art

Conventionally known optical disks for storing audio information andmoving picture information to be reproduced therefrom include compactdisks (CDs) and laser disks (LDs).

A CD is an optical disk having a diameter of 12 cm and stores digitaldata obtained by encoding music information using an encoding technologyreferred to as linear PCM. CDs have been utilized as a medium forstoring digital data for music applications.

An LD is an optical disk having a diameter of 30 cm and stores movingpicture information, along with audio information, in the form of analogsignals. LDs have been utilized as a medium for storing analog data forvideo applications such as movies.

Recently, new types of optical disks have been introduced. One of suchnew types of optical disks is an optical disk having a diameter of about12 cm which realizes long-time recording/storing and a sufficiently highquality by efficient compression of music information and/or movingpicture information including audio information. Another type of opticaldisk has a file structure with which data transmission with computersand communication devices is performed relatively easily.

Under such circumstances, an information storing medium which realizesstoring and reproduction of audio data with a higher quality thancompact disks have been demanded. As such an information storing medium,an optical disk in conformity with the DVD-Video format have beendeveloped and implemented. Such an optical disk realizes storing andreproduction of audio data of a high quality of linear PCM, 96kHz·24-bit sampling. However, with the DVD-Video format, it isimpossible to reproduce high quality linear PCM multi-surround audioinformation or higher quality audio information.

High quality audio data contains a large amount of data and thusrequires a high data transfer speed of audio data.

The present inventors have found, through many years of research anddevelopment on optical disks for storing high quality audio data, thatthe wait time before the start of reproduction of high quality audiodata causes various problems.

Before the start of reproduction of information stored on an opticaldisk, the wait time is required, which is the time period from when onesystem stream to be reproduced among one or more system streams storedon the optical disk is determined until the reproduction of the onesystem stream is started. The wait time is also referred to as the“start-up period”. A plurality of reproduction apparatuses havingdifferent levels of performance, such as data processing speed, usuallyhave different start-up periods.

In the case of, for example, high quality audio data having a streamstructure of the MPEG format, the start-up period includes time periodT_(s), time period T_(c), and time period T_(m). Time period T_(s) is aperiod required for the reproduction apparatus to seek to the position,on the optical disk, storing the audio data. Time period T_(c) is aperiod from when the audio data is input to a decoder until the firstcorrect decoded audio data is output from the decoder. Time period T_(c)includes a period for adjusting output timing of a system stream withreference to a PTS (Presentation Time Stamp) included in the systemstream and a period for examining whether or not the audio data includedin the system stream is correct. Time period T_(m) is a period fortransition of a muting circuit in an analog output section from a mutestate to a non-mute state.

In the case where a system decoder and an audio decoder are accommodatedin separate chassis or mounted on separate LSIs, the start-up period isfurther extended because adjustment of the output timing based on thePTS and the examination on whether or not the audio data is correct needto be performed separately.

When the start-up period is extended, malfunction that the output timingfor the system stream is not properly adjusted may undesirably occur ina specific reproduction apparatus and thus the leading audio data in thesystem stream is not reproduced.

When a plurality of reproduction apparatuses have different start-upperiods, the inter-tune interval of an optical disk varies in accordancewith the reproduction apparatus used. In such case, disk creators cannotuniformly set the inter-tune interval, which is significantlydisadvantageous to the disk creators and users.

SUMMARY OF THE INVENTION

According to one aspect of the invention, an information storing diskincludes at least one system stream stored thereon. The at least onesystem stream includes a silent cell for defining a silent period and anaudio cell for defining audio data to be reproduced after the silentperiod. The silent period is a period to be silent, which is from whenone system stream to be reproduced among at least one system stream isdetermined until reproduction of an audio cell included in the onesystem stream is started.

In one embodiment of the invention, the silent period includes a periodrequired by a reproduction apparatus after one system stream to bereproduced among at least one system stream is determined untilreproduction of the one system stream is started.

In one embodiment of the invention, the information storing disk furtherincludes information indicating the order of reproducing a plurality ofsystem streams. The silent period is a period to be silent, which isfrom when reproduction of one of the plurality of system streams isterminated until reproduction of an audio cell included in the nextsystem stream is started.

In one embodiment of the invention, the silent cell and the audio celleach include audio data encoded in an identical encode mode, and anoutput level of the audio data included in the silent cell issubstantially zero.

In one embodiment of the invention, the system stream includes a timestamp for defining output timing at a prescribed interval, apresentation period of the audio cell is determined based on adifference between a first time stamp and a final time stamp included inthe audio cell, and the silent period is determined based on adifference between a first time stamp and a final time stamp included inthe silent cell.

According to another aspect of the invention, a reproduction apparatusfor reproducing information stored on an information storing disk isprovided. The information storing disk including at least one systemstream stored thereon. The at least one system stream includes a silentcell for defining a silent period and an audio cell for defining audiodata to be reproduced after the silent period. The silent period is aperiod to be silent, which is from when one system stream to bereproduced among at least one system stream is determined untilreproduction of an audio cell included in the one system stream isstarted. The reproduction apparatus includes a reading section forreading a system stream to be reproduced among the at least one systemstream stored on the information storing disk, and a reproductionsection for reproducing a part of the silent cell and reproducing theaudio cell, from a point in the silent cell included in the read systemstream.

In one embodiment of the invention, the silent period includes a periodrequired by a reproduction apparatus after one system stream to bereproduced among at least one system stream is determined untilreproduction of the one system stream is started.

In one embodiment of the invention, the information storing disk furtherincludes information indicating the order of reproducing a plurality ofsystem streams. The silent period is a period to be silent, which isfrom when reproduction of one of the plurality of system streams isterminated until reproduction of an audio cell included in the nextsystem stream is started.

In one embodiment of the invention, the silent cell and the audio celleach include audio data encoded in an identical encode mode, and anoutput level of the audio data included in the silent cell issubstantially zero.

In one embodiment of the invention, the system stream includes a timestamp for defining output timing at a prescribed interval, apresentation period of the audio cell is determined based on adifference between a first time stamp and a final time stamp included inthe audio cell, and the silent period is determined based on adifference between a first time stamp and a final time stamp included inthe silent cell.

According to still another aspect of the invention, a reproductionmethod for reproducing information stored on an information storing diskis provided. The information storing disk includes at least one systemstream stored thereon. The at least one system stream includes a silentcell for defining a silent period and an audio cell for defining audiodata to be reproduced after the silent period. The silent period is aperiod to be silent, which is from when one system stream to bereproduced among at least one system stream is determined untilreproduction of an audio cell included in the one system stream isstarted. The reproduction method includes the steps of reading a systemstream to be reproduced among the at least one system stream stored onthe information storing disk, and reproducing a part of the silent celland reproducing the audio cell, from a point in the silent cell includedin the read system stream.

In one embodiment of the invention, the silent period includes a periodrequired by a reproduction apparatus after one system stream to bereproduced among at least one system stream is determined untilreproduction of the one system stream is started.

In one embodiment of the invention, the information storing disk furtherincludes information indicating the order of reproducing a plurality ofsystem streams. The silent period is a period to be silent, which isfrom when reproduction of one of the plurality of system streams isterminated until reproduction of an audio cell included in the nextsystem stream is started.

In one embodiment of the invention, the silent cell and the audio celleach include audio data encoded in an identical encode mode, and anoutput level of the audio data included in the silent cell issubstantially zero.

In one embodiment of the invention, the system stream includes a timestamp for defining output timing at a prescribed interval, apresentation period of the audio cell is determined based on adifference between a first time stamp and a final time stamp included inthe audio cell, and the silent period is determined based on adifference between a first time stamp and a final time stamp included inthe silent cell.

Thus, the invention described herein makes possible the advantages ofproviding an information storing disk for allowing a plurality ofreproduction apparatuses having different levels of performance, such asdata processing speed, to have an equal wait time (start-up period)before the reproduction of a system steam starts, and an apparatus and amethod for reproducing the system stream from the information storingdisk.

These and other advantages of the present invention will become apparentto those skilled in the art upon reading and understanding the followingdetailed description with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a data structure of a system stream 210 in conformity withthe MPEG format;

FIG. 2A shows the relationship between the audio packs A1 through A6,and the SCR and PTS included in each of the audio packs A1 through A6;

FIG. 2B shows timing for reproducing the system stream 210;

FIG. 3 shows a data structure of a system stream 310 stored on anoptical disk in a first example according to the present invention;

FIG. 4A shows the relationship between the audio packs S1 through S8 andA1 through A14, and the SCR and PTS included in each of the audio packsS1 through S8 and A1 through A14;

FIG. 4B shows timing for reproducing the system stream 310;

FIG. 5 shows a structure of a reproduction apparatus 400 in the firstexample according to the present invention;

FIG. 6A shows an external appearance of an optical disk in a secondexample according to the present invention;

FIG. 6B shows a cross section of the optical disk in the second exampleaccording to the present invention;

FIG. 6C is an enlarged cross-sectional view of the optical disk in thesecond example according to the present invention;

FIG. 6D shows pits formed in the optical disk in the second exampleaccording to the present invention;

FIG. 7A shows a track structure of the optical disk shown in FIG. 6A;

FIG. 7B shows a sector structure of the optical disk shown in FIG. 6A;

FIG. 8 shows a logical structure of the optical disk shown in FIG. 6A;

FIG. 9 shows a data structure of an audio manager;

FIG. 10 shows a data structure of an audio title set;

FIG. 11 shows an exemplary structure of an audio object (AOB):

FIG. 12 shows a data structure of PGC information and cell information;

FIG. 13 is a block diagram showing an internal structure of a DVDplayer, which is a reproduction apparatus;

FIG. 14 shows an example of PGC forming a title;

FIG. 15 shows an example of a program information;

FIG. 16 shows an example of cell information;

FIG. 17A shows a process for reproducing audio data without displaying astill picture;

FIG. 17B shows a process for reproducing audio data without displaying astill picture;

FIG. 18A shows a process for reproducing audio data while displaying astill picture;

FIG. 18B shows a process for reproducing audio data while displaying astill picture;

FIG. 19 shows a conventional process for reproducing audio data;

FIG. 20 shows a schematic flow for reproducing a program;

FIG. 21 shows a schematic flow for reproducing a leading audio cell;

FIG. 22 shows a flow for reproducing a silent cell;

FIG. 23 shows a flow for reproducing a continuously reproduced cell;

FIG. 24 is a DVD player and peripheral devices connected thereto; and

FIG. 25 shows a remote controller used for operating the DVD player.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described by way ofillustrative examples with reference to the accompanying drawings.

EXAMPLE 1

FIG. 1 shows a data structure of a system stream 210 in conformity withthe MPEG format. An optical disk can include at least one system stream210 stored thereon.

The system stream 210 can include a plurality of elementary streams. Theelementary streams are classified into a video elementary stream forstoring moving picture information and an audio elementary stream forstoring audio information. Each of the plurality of elementary streamsis divided into a plurality of packs. Each of the plurality of packs hasa length of 2 Kbytes.

In the example shown in FIG. 1, the system stream 210 is formed of oneaudio elementary stream. The system stream 210 includes a plurality ofaudio packs 220. The plurality of audio packs 220 are respectivelyrepresented by denotations A1 through A14.

Each of the plurality of audio packs 220 includes a pack header 222, apacket header 224 and a data field 226.

In the pack header 222, data in conformity with the MPEG format such as,for example, a pack start code, an SCR (System Clock Reference) and anMUX (multiplex) rate are described.

In the packet header 224, data in conformity with the MPEG format suchas, for example, a stream ID, a packet length, an STD (System TargetDecoder) buffer scale size, and a PTS (Presentation Time Stamp) aredescribed. The packet header 224 includes an area for storing a DTS(Decoding Time Stamp) which defines decoding timing of data as requiredby the MPEG format, but such an area is not used for audio elementarystream.

The stream ID described in the packet header 224 is a code indicatingthe type of data stored in the data field 226. For example, when thedata stored in the data field 226 is audio data, code “10111101” isdescribed in the packet header 224 as the stream ID.

A sub stream ID is described in the first eight bits of the data field226. The upper five bits of the eight bits of the sub stream ID indicatean encode type. The encode format can be LPCM, AC3, DTS, or the like.The lower three bits of the eight bits of the sub stream ID indicate anidentification number of the sub stream. The identification number isany one of 0 through 7. A system stream can include a maximum of 8 audioelementary streams. The maximum of 8 audio elementary streams can beidentified using the identification numbers.

The SCR in the pack header 222 and the PTS in the packet header 224 areused for adjusting the synchronization between decoding of the audiopack and decoding of a sub video pack.

FIG. 2A shows the relationship between the system stream 210 includingthe plurality of audio packs A1 through A6, and the SCR and the PTSincluded in each of the audio packs A1 through A6.

When a reproduction apparatus reproduces the system stream 210 stored onthe optical disk, the reproduction apparatus sets the SCR included inthe leading audio pack A1 in the system stream 210 as an initial valueof an STC (System Time Clock), which is a reference clock. Then, thereproduction apparatus inputs the audio packs A2 through A6 followingthe audio pack A1 to a decoder at the timing indicated by the SCR withreference to the STC. The decoder decodes the input audio packs. Thedecoded audio packs are externally output from the decoder at the timingindicated by the PTS.

The present inventors analyzed problems which can occur when highquality audio data is reproduced using the data structure of the systemstream shown in FIG. 1 and the reproduction method shown in FIG. 2A. Theresults of analysis will be described below.

The inventors have noticed that the timing for initiating the STC (i.e.,the timing for resetting the STC) should be a point of attention. Asdescribed above, in accordance with the reproduction method shown inFIG. 2A, the STC is reset when the leading audio pack A1 in the systemstream 210 is reproduced. Before the reproduction of the leading audiopack A1 starts, a wait time for preparing for the reproduction isrequired. Since the wait time varies in accordance with the processingcapability of the reproduction apparatus used, the time for reproducingthe leading audio pack A1 varies in accordance with the type ofreproduction apparatus. As a result, the time for resetting the STC alsoundesirably varies in accordance with the type of reproductionapparatus.

This point will be described in more detail.

Reproduction of information stored on an optical disk requires a waittime from when one system stream to be reproduced among one or moresystem steams stored on the optical disk is determined until thereproduction of the one system stream is started. The wait time variesin accordance with the capability of the reproduction apparatus, andgenerally tends to be shorter in higher-level apparatuses and longer inlower-level apparatuses. The wait time is also referred to as the“start-up period”.

In the case of, for example, high quality audio data having a streamstructure of the MPEG format, the start-up period includes time periodT_(s), time period T_(c), and time period T_(m). Time period T_(s) is aperiod required for the reproduction apparatus to seek to a position, onthe optical disk, storing the audio data. Time period T_(c) is a periodfrom when the audio data is input to a decoder until the decoded audiodata is output from the decoder. Time period T_(c) includes a period foradjusting output timing of a system stream with reference to a PTSincluded in the system stream and a period for examining whether or notthe audio data included in the system stream is correct. Since theexamination on the audio data is usually performed before the audio datais output in accordance with the PTS, time period T_(c) equals to aperiod obtained by subtracting the SCR from the PTS. Time period T_(m)is a period for transition of a muting circuit in an analog outputsection from a mute state to a non-mute state.

A plurality of reproduction apparatuses having different levels ofperformance, such as data processing speed, have different start-upperiods because time period T_(s), time period T_(c), and time periodT_(m) vary in accordance with the type of reproduction apparatus.

For example, reproduction apparatuses commercially available currentlyhave time period T_(s) (seek period) of several ten milliseconds toabout 500 milliseconds. However, time period T_(s) depends on, forexample, the torque of a motor for rotating the optical disk mounted onthe reproduction apparatus. Accordingly, there can be reproductionapparatuses having time period T_(s) of a maximum of several seconds. Ascan be appreciated from these values, time period T_(s) varies by theorder of several hundred milliseconds in accordance with the type ofreproduction apparatus.

Time period T_(c) depends on the algorithm adopted by the reproductionapparatus for decoding. Time period T_(c) varies by the order of severalhundred milliseconds in accordance with the type of adopted algorithm.

Time period T_(m) also varies by the order of several hundredmilliseconds in accordance with the performance of the circuit mountedon the reproduction apparatus.

FIG. 2B shows the timing for starting the reproduction of the samesystem stream 210 in two reproduction apparatuses #1 and #2 of differenttypes.

Reproduction apparatus #1 has a lower level of performance than that ofreproduction apparatus #2. Reproduction of the system stream 210 byreproduction apparatus #1 requires a longer start-up period thanreproduction of the system stream 210 by reproduction apparatus #2. Inother words, start-up period #1>start-up period #2.

In reproduction apparatus #1, after start-up period #1, the STC is resetbased on the SCR of the leading audio pack A1 at time a2. As a result,the reproduction of the system stream 210 starts at time a2. In contrastin reproduction apparatus #2, after start-up period #2, the STC is resetbased on the SCR of the leading audio pack A1 at time a1. As a result,the reproduction of the system stream 210 starts at time a1.

The present inventors have found that the time for starting thereproduction of the system stream varies in accordance with the type ofreproduction apparatus. In the example shown in FIG. 2B, time a2 whenthe reproduction apparatus #1 starts the reproduction of the leadingaudio pack A1 in the system stream 210 corresponds to a time when thereproduction apparatus #2 starts the reproduction of the fifth audiopack A5 in the system stream 210.

Hereinafter, a data structure of a system stream and a method forreproducing the system stream according to the present invention will bedescribed. A data structure of a system stream and a method forreproducing the system stream according to the present invention aresuitable for reproducing high quality audio data.

FIG. 3 shows a data structure of a system stream 310 stored on anoptical disk in a first example according to the present invention.

In the example shown in FIG. 3, the system stream 310 is formed of oneaudio elementary stream. The system stream 310 includes a silent cell312 for defining a silent period and an audio cell 314 for defining theaudio data to be reproduced after the silent period. The silent cell 312and the audio cell 314 each include a plurality of audio packs 320.

The silent period is defined as a period to be silent, which is fromwhen one system stream 310 to be reproduced among at least one systemstream 310 is determined until the reproduction of an audio cell 314included in the one system stream 310 is started. In the case where theoptical disk includes information indicating the order of reproducing aplurality of system steams stored thereon, the silent period is definedas a period to be silent, which is from when the reproduction of one ofthe plurality of system streams is terminated until the reproduction ofan audio cell included in the next system stream is started.

In the example shown in FIG. 3, the silent cell 312 includes audio packsS1 through S8, and the audio cell 314 includes audio packs A1 throughA14. The data structure of the audio packs S1 through S8 and the datastructure of the audio packs A1 through A14 are identical with the datastructure of the audio pack 220 shown in FIG. 1. The silent cell 312 caninclude N-piece audio packs, and the audio cell 314 can include M-pieceaudio packs. N and M are each an arbitrary integer one or greater.

The audio data contained in the audio packs S1 through S8 and the audiodata contained in the audio packs A1 through A14 are encoded in anidentical encoding mode since the silent cell 312 and the audio cell 314are included in one MPEG stream. The identical encoding mode refers tothat all the encoding attributes such as encode format (e.g., LPCM, AC3)and sampling rate are identical.

The output level of the audio data contained in the audio packs S1through S8 is substantially zero. In other words, audio data whichsubstantially represents silence when being output is stored in thesilent cell 312. It is not essential for defining the silent period thatthe output level of the audio data stored in the silent cell 312 issubstantially zero. As described below, even when the audio data storedin the silent cell 312 is not substantially zero, silence can berealized during the silent period by controlling a muting circuit.

The PTS contained in each of the audio packs A1 through A14 of the audiocell 314 defines the timing for outputting the decoded audio packs fromthe decoder. Accordingly, the difference between the PTS contained inthe leading audio pack A1 of the audio cell 314 and the PTS contained inthe final audio pack A14 of the audio cell 314 nearly equals to apresentation period of the audio cell 314. Thus, the presentation periodof the audio cell 314 is determined based on the difference between thefirst PTS and the final PTS in the audio cell 314.

The PTS contained in each of the audio packs S1 through S8 of the silentcell 312 defines the timing for outputting the decoded audio packs fromthe decoder. The PTS in each of the audio packs S1 through S8 does notdefine a presentation period of the silent cell 312 but defines thesilent period before starting the reproduction of the system stream 310including the silent cell 312. Accordingly, the difference between thePTS contained in the leading audio pack S1 of the silent cell 312 andthe PTS contained in the first audio pack A1 of the audio cell 314continued after the silent cell 312 equals to the silent period of thesystem stream 310. Thus, the silent period of the system stream 310 isdetermined based on the difference between the first PTS in the silentcell 312 and the first PTS in the audio cell 314 continued after thesilent cell 312.

The silent period of the system stream 310 defined by the silent cell312 is utilized by the reproduction apparatus as the period forabsorbing a variation in the start-up period which depends on the typeof reproduction apparatus. The length of the silent period ispredetermined so as to include the start-up period. In a preferredembodiment of the invention, the length of the silent period ispredetermined so as to include the longest start-up period of thestart-up periods of the reproduction apparatuses which can be producedin conformity with the MPEG format.

When a reproduction apparatus is given, the start-up period of thereproduction apparatus is pre-calculated. For example, seek period T_(s)is calculated from the seek distance. Time period T_(c) and time periodT_(m) are fixed with respect to each reproduction apparatus.Accordingly, the start-up period of the reproduction apparatus iscalculated as the sum of seek period T_(s), time period T_(c) and timeperiod T_(m).

FIG. 4A shows the relationship between the system stream 310 includingthe plurality of audio packs S1 through S8 and A1 through A14, and theSCR and the PTS included in each of the plurality of audio packs S1through S8 and A1 through A14.

When a reproduction apparatus reproduces the system stream 310 stored onthe optical disk, the reproduction apparatus sets the SCR included inthe leading audio pack S1 of the silent cell 312 as an initial value ofan STC (system time clock), which is a reference clock. Then, thereproduction apparatus inputs the audio packs S2 through S8 and A1through A14 following the audio pack S1 to a decoder at the timingindicated by the SCR with reference to the STC. The decoder decodes theinput audio packs. The decoded audio packs are externally output fromthe decoder at the timing indicated by the PTS.

FIG. 4B shows the timing for starting the reproduction of the samesystem stream 310 in two reproduction apparatuses #1 and #2 of differenttypes.

Reproduction apparatus #1 has a lower level of performance than that ofreproduction apparatus #2. Reproduction of the system stream 310 byreproduction apparatus #1 requires a longer time period T_(s) thanreproduction of the system stream 310 by reproduction apparatus #2. Inother words, time period T_(s)#1>time period T_(s)#2.

Reproduction apparatus #1 is controlled so that the reproduction of thesystem stream 310 starts at time t2 after time period T_(s)#1. As shownin FIG. 4A, the first audio pack among the audio packs having an SCR ofa larger value than that of time t2 is audio pack S6. Accordingly, theSTC is reset based on the SCR of the sixth audio pack S6 of the silentcell 312. As a result, the decoding of the audio data starts from somepoint in the silent cell 312, so that audio data is allowed to be outputafter time period T_(c)#1.

It should be noted that in reproduction apparatus #1, even though theaudio data is decoded, the audio data is not output before time t3,since the muting circuit is in the mute state before time t3. Timeperiod T_(m)#1 starts at time t3. During time period T_(m)#1, the mutingcircuit is controlled to be transitioned from the mute state to thenon-mute state. At time k, when time period T_(m)#1 terminates, themuting circuit is in the non-mute state. Accordingly, the audio data ofthe audio packs A1 through A14 reproduced from time k is output.

Reproduction apparatus #2 is controlled so that the reproduction of thesystem stream 310 starts at time t1 after time period T_(s)#2. As shownin FIG. 4A, the first audio pack among the audio packs having an SCR ofa larger value than that of time t1 is audio pack S3. Accordingly, theSTC is reset based on the SCR of the third audio pack S3 of the silentcell 312. As a result, the decoding of the audio data starts from somepoint in the silent cell 312, so that audio data is allowed to be outputafter time period T_(c)#2.

It should be noted that in reproduction apparatus #2, even though theaudio data is decoded, the audio data is not output before time t4,since the muting circuit is in the mute state before time t4. Timeperiod T_(m)#2 starts at time t4. During time period T_(m)#2, the mutingcircuit is controlled to be transitioned from the mute state to thenon-mute state. At time k, when time period T_(m)#2 terminates, themuting circuit is in the non-mute state. Accordingly, the audio data ofthe audio packs A1 through A14 reproduced from time k is output.

As described above, in reproduction apparatus #1, reproduction startsfrom the audio pack S6 of the silent cell 312; whereas in reproductionapparatus #2, reproduction starts from the audio pack S3 of the silentcell 312. In both of reproduction apparatuses #1 and #2, audio output issuppressed during the silent period. Thus, the silent period of thesystem stream 310 can always be the same regardless of the type ofreproduction apparatus.

Even when the muting circuit malfunctions, audio output during thesilent period can be prevented by setting the audio data contained ineach of the audio packs S1 through S8 of the silent cell 312 tosubstantially zero. During the period in which the silent cell 312 isreproduced, the audio output can be suppressed regardless of theoperating state of the muting circuit.

FIG. 5 shows a structure of a reproduction apparatus 400 in the firstexample according to the present invention.

An optical disk 410 includes at least one system stream 310 (FIG. 3)stored thereon. The reproduction apparatus 400 reproduces at least onesystem stream 310 stored on the optical disk 410. The structure of thesystem stream 310 is as shown in FIG. 3.

As the optical disk 410, an arbitrary information storing medium can beused. For example, the optical disk 410 can be a DVD.

The reproduction apparatus 400 includes a reading section 420 forreading the system stream 310 to be reproduced among the at least onesystem stream 310, and a reproduction section 430 for reproducing a partof the silent cell 312 and the audio cell 314 from some point in thesystem stream 310 read by the reading section 420.

The reproduction section 430 includes a decoder 432 for decoding thesystem stream 310, an output section 434 for outputting the decodedsystem stream 310, and a muting circuit 436 for determining whether ornot the output of the audio data needs to be muted.

The operation of the reading section 420 and the operation of thereproduction section 430 are controlled by a control section 438.

With reference to FIG. 5, the operation of the reproduction apparatus400 will be described. Time period T_(s) required for the reproductionapparatus 400 to seek to the position on the optical disk 410 at whichthe audio data is stored, time period T_(c) from when the audio data isinput to the decoder 432 until the decoded audio data is output from thedecoder 432, and time period T_(m) for transition of the muting circuit436 from the mute state to the non-mute state are assumed to bepre-calculated. It is also assumed that the silent period is defined soas to include time period T_(s), time period T_(c) and time period T_(m)by the silent cell 312 of the system stream 310 stored on the opticaldisk 410. Such assumptions are possible as described above.

The reading section 420 reads the system stream 310 to be reproducedamong the at least one system stream 310 stored on the optical disk 410in response to an instruction from the control section 438. The systemstream 310 to be reproduced is selected by, for example, the user. Suchselection is performed by, for example, selecting a desired item fromthe menu displayed on a TV (not shown) connected to the reproductionapparatus 400. Alternatively, the system stream 310 to be reproduced canbe automatically determined by the reproduction apparatus 400. Suchautomatic determination is executed by a program executed by the controlsection 438 of the reproduction apparatus 400.

The control section 438 compares the SCR and seek period T_(s) of eachof the audio packs S1 through S8 included in the silent cell 312 of thesystem stream 310 read by the reading section 420, thereby determiningthe first audio pack among the audio packs having an SCR of a largervalue than a value indicating the termination time of seek period T_(s)(e.g., audio pack A6). The control section 438 resets the STC based onthe SCR of the audio pack A6. As a result, the audio stream 310 is inputto the decoder 432 from the audio pack A6 located at some point in thesilent cell 312.

The decoder 432 decodes the input audio packs. The audio packs decodedby the decoder 432 are output from the decoder 432 in accordance withthe output timing defined by the PTS of each of the audio packs. Thetime when the decoded audio pack is output generally is the time whentime period T_(c) has been passed after time period T_(s) is terminated.

The output section 434 outputs the audio data included in the decodedaudio packs.

The muting circuit 436 determines whether or not the audio data outputfrom the outputs section 434 needs to be muted. The control section 438controls the muting circuit 436 to mute the audio data output from theoutput section 434 until the start of time period T_(m) and controls themuting circuit 436 to be transitioned from the mute state to thenon-mute state during time period T_(m).

Thus, audio output is suppressed during the silent period of the systemstream 310.

The silent period defined by the silent cell 312 is defined so as toabsorb the start-up period which is inherent to reproductionapparatuses. Accordingly, even when the system stream 310 is reproducedby a reproduction apparatus other than the reproduction apparatus 400,audio output is suppressed during the silent period of the system stream310.

EXAMPLE 2

A multimedia information storing medium in a second example according tothe present invention will be described.

(1) Physical Structure of the Optical Disk

FIG. 6A shows an external appearance of a DVD 107, which is a multimediaoptical disk. FIG. 6B shows a cross-section of the DVD 107 taken alongline A-A′ in FIG. 6A. FIG. 6C is an enlarged cross-sectional view ofportion B shown in FIG. 6B.

As shown in FIG. 6B, the DVD 107 is formed by sequentially laminating afirst transparent substrate 108, an information layer 109, an adhesivelayer 110, a second transparent substrate 111, and a print layer 112 onwhich a label is to be printed in this order.

The first transparent substrate 108 and the second transparent substrate111 are reinforcement substrates formed of the same material. In theexample shown in FIG. 6B, these substrates each have a thickness ofabout 0.6 mm. These substrates can each have a thickness in the rangebetween about 0.5 mm and about 0.7 mm.

The adhesive layer 110 is provided between the information layer 109 andthe second transparent substrate 111 in order to adhere the informationlayer 109 to the second transparent substrate 111.

On the face of the information layer 109 in contact with the firsttransparent substrate 108 is formed a reflective film (not shown) formedof a thin metal film or the like. By using a molding technique, a highdensity of convex and concave pits are formed in the reflective film.

FIG. 6D shows the shapes of pits formed in the reflective film. In theexample shown in FIG. 6D, each pit has a length of 0.4 μm to 2.054 μm. Aspiral track is formed in the DVD 107. The pits are formed alongside thespiral track so as to be at a distance of 0.74 μm from the spiral trackin a radial direction of the DVD 107. Thus, an array of pits are formedalong the spiral track.

When a light beam 113 is radiated toward the DVD 107, a light spot 114is formed on the information layer 109 as shown in FIG. 6C. Theinformation stored on the DVD 107 is detected as variation in thereflectance of the portion of the information layer 119 which isilluminated by the light spot 114.

The diameter of the light spot 114 of the DVD 107 is about {fraction(1/1.6)} times the diameter of a light spot on a CD and because thenumerical aperture (NA) of an object lens for DVDs is larger than thenumerical aperture of an object lens for compact disks and because thewavelength λ of a light beam for DVDs is shorter than the wavelength λof a light beam for CDs.

A DVD having the above-described physical structure can store about 4.7Gbytes of information on one side. A storing capacity of about 4.7Gbytes is nearly 8 times the storing capacity of a conventional CD. Sucha large storing capacity of DVDs can greatly improve the quality ofmoving pictures and also greatly extend the reproducible time period ofmoving pictures. Whereas the reproducible time period of a conventionalvideo CD is 74 minutes, a DVD boasts of a reproducible time period of 2hours or more.

The fundamental technology which realizes such a large storing capacitylies in reduction of the spot diameter D of a light beam. The spotdiameter D is calculated from the formula: spot diameter D=laserwavelength λ/numerical aperture NA of the object lens. Accordingly, thespot diameter D can be minimized by decreasing the laser wavelength λand increasing the numerical aperture NA of the object lens. It shouldbe noted, however, that increasing the numerical aperture NA of theobject lens can result in coma aberration due to the relative slant ofthe optical axis of the light beam with respect to the face of the disk(i.e., “tilt”). In the case of DVDs, the coma aberration is minimized byreducing the thickness of a transparent substrate. However, reducing thethickness of a transparent substrate can result in another problem oflower mechanical strength of the disk. In the case of DVDs, the strengthof the transparent substrate is reinforced by attaching anothersubstrate to the transparent substrate, thereby overcoming the problemsassociated with the mechanical strength of the disk.

A red semiconductor laser having a short wavelength of 650 nm and anobject lens having a large numerical aperture (NA) of about 0.6 mm areused to read the information stored on a DVD. By employing a thintransparent substrate having a thickness of about 0.6 mm in addition tothe above-mentioned laser and object lens, it is possible to store about4.7 Gbytes of information on one side of an optical disk having adiameter of 120 mm.

FIG. 7A schematically illustrates a spiral track 20 formed from theinner periphery toward the outer periphery of the information layer 109of the DVD 107. The spiral track 20 is divided into prescribed unitsreferred to as sectors. In FIG. 7A, the respective sectors arerepresented by denotations S1, S2, . . . , S99, and S100. Theinformation stored on the DVD 100 is read on a sector-by-sector basis.

FIG. 7B shows an internal structure of a sector, where the sectorincludes a sector header region 21, a user data region 22, and an errorcorrection code storage region 23.

The sector header region 21 stores a sector address for identifying thesector and an error detection code thereof. Based on these sectoraddresses, a disk reproduction apparatus determines one of a pluralityof sectors from which information should be read.

The user data region 22 stores a 2 Kbyte long data string.

The error correction code storage region 23 stores error correctioncodes for the sector header region 21 and the user data region 22included in the same sector. A disk reproduction apparatus performserror detection by using the error correction codes and performs errorcorrection based on the error detection results, thereby securingreliability of data reading.

(2) Logical Structure of the Optical Disk

FIG. 8 shows a logical structure of the DVD 107. As shown in FIG. 8, theregion of the DVD 107 is divided into a lead-in region 31, a volumeregion 32, and a lead-out region 33. These regions can be identified byidentification information included in sector addresses of physicalsectors. The physical sectors are arrayed in an ascending order based ontheir sector addresses.

In the lead-in region 31, data for stabilizing the operation of areproduction apparatus at the beginning of read, for example, is stored.

No meaningful data is stored in the lead-out region 33. The lead-outregion 33 is used for informing the disk reproduction apparatus of thetermination of reproduction.

The volume region 32 stores digital data corresponding to anapplication. The physical sectors included in the volume region 32 aremanaged as logical blocks. The logical blocks are identified by thesequential numbers (logical block numbers) respectively assigned to thephysical sectors after the first physical sector (designated as the 0thphysical sector) in the volume region 32.

As shown in FIG. 8, the volume region 32 is subdivided into a volumefile management region 32 a and an audio zone region 32 c.

The volume file management region 32 a stores file system managementinformation for managing a plurality of logical blocks as files inaccordance with ISO13346. The file system management information isinformation indicating the correspondence between the name of each of aplurality of files and the addresses of the logical blocks occupied bythat file. A disk reproduction apparatus achieves file-by-file access tothe optical disk based on the file system management information.Specifically, the disk reproduction apparatus refers to the file systemmanagement information to obtain the addresses of the logical blockscorresponding to a given file name, and accesses the logical blocksbased on these addresses. As a result, the digital data contained in adesired file can be read.

The audio zone region 32 c stores audio manager 900 and one or moreaudio title sets 800.

The audio title set 800 contains a plurality of pieces of audio data andmanagement information for managing the order of reproducing theplurality of pieces of audio data. The audio title set 800 has a datastructure which allows for management of the audio data in units whichare referred to as audio titles. Typically, an audio title correspondsto a music album containing one or more tunes.

(3) Data Structure of the Audio Zone Region 32 c

The audio zone region 32 c stores audio manager 900 and one or moreaudio title sets 800.

(3.1) Data Structure of the Audio Title Set 800

FIG. 10 shows a data structure of the audio title set 800. The audiotitle set 800 includes a plurality of audio objects (hereinafter,referred to as “AOBs”) 802, audio title set information (ATSI) 801 formanaging the order of reproducing the plurality of AOBs 802, and audiotitle set information backup (ATSI_BUP) 804 which is backup data of theaudio title set information 801. In the following description, an “audiotitle set” will occasionally be referred to as an “ATS”.

(3.1.1) Data Structure of the AOB 802

The AOB 802 is packetized into 2 Kbytes. The AOB 802 stores data in theLPCM format, AC3 format, MPEG Audio format (see ISO/IEC DIS 13818-3:July, 1996), DTS format (see DTS Coherent Acoustics “Delivering highquality multichannel sound to the consumer” presented at the 100thConvention, May 11-14, 1996 Copenhagen AES) or SDDS format (see SDDSSpecification for Disc (Version 1.0)-Digital audio multi-channel coding,Sony Corporation). In the case of the LPCM format, the sample bit is 16,20, or 24 bits, with a sampling frequency of 48 kHz, 96 kHz, 192 kHz,44.1 kHz, 88.2 kHz, or 176.4 kHz.

(3.1.2) Data Structure of the Audio Title Set Information 801

The audio title set information (ATSI) 801 includes information formanaging the order of reproducing the AOBs 802. The order of reproducingthe AOBs 802 is designated by a program chain (PGC), as in the case ofvideo objects (VOBs). Different PGCs can define different orders ofreproduction of AOBs.

As shown in FIG. 10, the audio title set information (ATSI) 801 includesan ATS management table (ATSI_MAT) 811 and a PGC management informationtable (ATS_PGCIT) 812.

The ATS management table 811 serves as header information of the audiotitle set information 801. The ATS management table 811 includes apointer indicating a region in which the AOB 802 is stored, a pointerindicating a region in which the PGC management information table 812 isstored, and attribute information on the AOB 802. In the case where astill picture is stored on the DVD 107, the ATS management table 811also includes attribute information and the like of the still picture.

The PGC management information table (ATS_PGCIT) 812 includes ATS PGCinformation table information (ATS_PGCITI) 831, a plurality of ATS PGCinformation search pointers (ATS_PGCI_SRPs) 832, and a plurality of PGCinformation (ATS_PGCI) units 833.

The ATS PGC information search pointers (ATS_PGCI_SRPs) 832 are indicesfor a plurality of PGCs stored in the PGC management information table812 and designate the PGC information to be executed first on atitle-by-title basis.

Each of the PGC information units describes positions on the opticaldisk 107 where one or more audio objects and the order of reproductionthereof. Reproduction of the same audio object can be described bydifferent PGC information. Specifically, the PGC information includes“ATS PGC general information (ATS_PGC_GI)”, “ATS program informationtable (ATS_PGIT)”, and “ATS cell reproduction information table(ATS_C_PBIT)”.

FIG. 12 shows a data structure of the PGC information. As shown in FIG.12, “ATS PGC general information (ATS_PGC_GI)” includes the number ofprograms and the number of cells included in the PGC information, thereproduction time period of the PGC, and information on pointers to the“ATS program information table (ATS_PGIT)” and to “ATS cell reproductioninformation table (ATS_C_PBIT)”.

The “ATS program information table (ATS_PGIT)” includes “programphysical allocation information” indicating whether or not the AOB ofeach program and the AOB of the previous program are recorded atphysically discontinuous positions on the optical disk, “program timeattribute information” indicating whether or not the time information ofthe AOB is continuous with the time information of the previous AOB,“program start cell number” indicating the first cell number forming theprogram, “program still picture flag” indicating whether or not theprogram includes a still picture, “reproduction start audio cell time”indicating the first time information of the first audio cell includedin the program, “program total reproduction time period” indicating thereproduction time period of the program, and “audio pause time period”indicating the silent period until the reproduction of the audio cell ofthe program starts.

The “ATS cell reproduction information table (ATS_C_PBIT)” stores cellinformation forming the AOB to be reproduced. Specifically, the AOBincludes “cell index number” indicating the order of cells included inthe program, “cell type” indicating the attribute of the cell (i.e.,whether the cell is a still picture cell, a silent cell or an audiocell), “cell start address” indicating the start address of the cell inthe form of a relative address with respect to the first pack of the AOBof the ATS including the cell, and “cell termination address” indicatingthe final address of the cell in the same manner.

FIG. 11 shows an exemplary structure of the AOB. The AOB is a part of anMPEG2 stream and includes a still picture cell including a still picturepack, a silent cell including an audio pack including substantiallysilent audio data, and an audio cell including an audio pack of audiodata forming a tune. The AOB includes one or more audio cells and maynot include a still picture cell or a silent cell. Still picture cellsare never continuous with each other and silent cells are nevercontinuous with each other. A still picture cell is always followed by asilent cell or an audio cell. A silent cell is always followed by anaudio cell. In the example shown in FIG. 11, audio cells and silentcells exist and are physically continuous. Time information is alsocontinuous; i.e., the “program physical allocation information” has avalue representing “continue”, and the “program time attributeinformation” also has a value representing “continue”.

In FIG. 11, the line passing through points A through G represents achange in the value of the time information (i.e., PTS) of AOB. Point Arepresents a value of the PTS of the still picture cell. Point Brepresents a value of the first PTS of a silent cell. Point C representsa value of the first PTS of an audio cell. Thus, the PTS of a silentcell is continuous to the PTS of an audio cell, and there is no dataunderflow gap, as referred to with respect to the MPEG2 stream, betweenthe silent cell and the audio cell. Point B, at which the value of thePTS of the silent cell is larger than the value of the PTS of the stillpicture cell, represents that a still picture in the still picture cellis displayed before the reproduction of the silent cell starts. The PTSof the next still picture cell is represented by point D, and the PTS ofthe next silent cell is represented by point E. In the case where thePTS of the still picture cell and the PTS of the silent cell have anequal value, the reproduction of the silent cell starts simultaneouslywhen the still picture is displayed. The difference between the firstPTS of the next audio cell at point F and the final PTS of the audiocell at point D is an “audio pause time period”. Since the gap betweenthe PTS's needs to be 0.7 seconds or less as specified by MPEG2, thedifference at point B between the first PTS of the silent cell and thePTS of the still picture cell, and the difference at point D between thefirst PTS of the still picture cell and the final PTS of the audio cellneed to fulfill such a condition.

FIG. 14 shows an exemplary PGC forming a title. The example shown inFIG. 14 includes five programs. Programs #1 and #2 correspond to AOB #1,and programs #3, #4 and #5 correspond to AOB #2. On the informationstoring medium, AOB #1 is recorded after AOB #2. Programs #1 and #2 bothinclude a still picture cell and a silent cell, and program #2 includestwo audio cells. Programs #3 and #4 includes only a silent cell, andprogram #5 includes only an audio cell.

In the case where all the audio cells each have a reproduction timeperiod of 60 seconds (5,400,000 in PTS), all the silent cells each havea reproduction time period of 1 second (90,000 in PTS), and the PTS ofthe silent cell has the same value as that of the first PTS of thesilent cell, program information can be described as shown in FIG. 15.Under the conditions that the size of the still picture data is about1.88 Mbits and the audio data is 48 kHz, 16 bit sampling with 2channels, the number of the still picture packs is 112, the number ofthe silent cell packs is 96, and the number of the audio cell packs is5760 as shown in FIG. 16.

The audio title set has been described. Next, with reference to FIG. 9,the audio manager will be described.

(3.2) Data Structure of the Audio Manager 900

The audio manager 900 is information for controlling the reproductionwhich is to be first referred to for performing audio-orientedreproduction of the information on the optical disk by a reproductionapparatus.

FIG. 9 shows a data structure of the audio manager 900.

The audio manager 900 includes “audio manager information (AMGI)”, “VOBfor audio manager menu (AMGM_VOBS)”, and “audio manager informationbackup (AMGI_BUP)”.

The “audio manager information (AMGI)” includes “audio managerinformation management table (AMGI_MAT)” including attribute informationand pointer information, “audio title management information” indicatingthe number of audio titles and the like, “audio title search pointer(ATT_SRP)” indicating search information on the audio titles, and “audiomanager menu PGC management information table (AMGM_PGCI_UT)” indicatingPGC information for audio manager menu.

The “audio title search pointer (ATT_SRP)” includes “audio title type”indicating the type of each title, “number of programs in the titles”indicating the number of programs included in the titles, “titlereproduction time period” indicating the reproduction time period of thetitles, “ATS title number” indicating the set number of the ATS to whicheach title belongs, “ATS title number” indicating the title number ofeach title in the ATS, and “ATS address” indicating the address of theATS to which each title belongs.

The audio zone region and the DVD as a multimedia optical disk have beendescribed. Next, a reproduction apparatus according to the presentinvention will be described.

First, an external appearance of a DVD player, which is a reproductionapparatus for multimedia optical disks will be described. FIG. 24 showsexternal appearances of a DVD player 1, a TV monitor 2 and a remotecontroller 91.

The DVD player 1 has an opening in a front face of a chassis thereof,and includes a driving mechanism for setting an optical disk in thedepth direction of the opening.

Provided on the front face of the DVD player 1 is a remote controlreceiving section 92 having a light receiving element for receivinginfrared rays emitted by the remote controller 91. When an operatoroperates a remote controller held in his/her hand, the remote controlreceiving section 92 sends an interrupt signal indicating that a keysignal has been received.

Provided on a rear face of the DVD player 1 are video and audio outputterminals. A video signal reproduced from the DVD can be output to thelarge TV monitor 2 for home use by connecting an AV cord to the videoand audio output terminals. Thus, the operator can enjoy the videoreproduced from the DVD on a large TV of, for example, 33 inches or 35inches. As can be appreciated from the above description, the DVD player1 in this example is not used in the state of being connected to apersonal computer but is used with the TV monitor 2 as an electronicappliance for home use.

The remote controller 91 includes a spring-loaded keypad on a surface ofa casing thereof, and outputs a code corresponding to a pressed key byinfrared rays. FIG. 25 shows an operation panel of the remote controller91. The “POWER” key on the operation panel is for turning ON or OFF theDVD player 1. The “MENU” key is used for retrieving the volume menu ofthe optical disk during reproduction of the program chain. Ten keys areused for, for example, chapter-jumping the movie or selecting musictunes. Upward, downward, leftward and rightward cursor keys are used forselecting items. The “ENTER” key is used for confirming the itemselected by the cursor. When the cursor is moved on the items by theupward, downward, leftward and rightward cursor keys, the item on whichthe cursor is positioned is displayed with a select color of item colorinformation of the management information pack. When the item isconfirmed by the “ENTER” key, the item is displayed with a confirmationcolor. In addition, there are keys which are common with other AVapparatuses such as, for example, “PLAY”, “STOP”, “PAUSE”, “FORWARD” and“REWIND” keys.

Next, the structure of the DVD player, which is a reproduction apparatusfor multimedia optical disks will be described.

FIG. 13 is a block diagram of an internal structure of the DVD player.The DVD player includes a driving mechanism 81, an optical pickup 82, amechanism control section 83, a signal processing section 84, an AVdecoder 85, a remote control receiving section 92 and a system controlsection 93.

The driving mechanism 81 includes a table on which an optical disk isset and a spindle motor for rotating the optical disk which is set onthe table. The table is structured to move to be in and out of thechassis by an eject mechanism not shown. When the table is out of thechassis, the operator sets an optical disk onto the table. When theoptical disk is set on the table and the table is moved back to thechassis, the optical disk is loaded on the DVD player.

The mechanism control section 83 controls a mechanical system includingthe motor 81 for driving the disk and the optical pickup 82 for readinga signal recorded on the disk. Specifically, the mechanism controlsection 83 adjusts the motor speed in accordance with the position ofthe track indicated by the system control section 93. The mechanismcontrol section 83 also controls an actuator of the optical pickup 82 tomove the optical pickup 82. When the accurate track is detected by servocontrol, the mechanism control section 83 controls the optical disk towait until a desired physical sector on the rotating optical diskreaches the position of the optical pickup 82. Then, signals arecontinuously read from the desired position.

The signal processing section 84 processes the signal read from theoptical pickup 82 with, for example, amplification, waveform shaping,binarization, demodulation, and error correction to convert the signalinto a digital data stream, and then stores the resultant data stream ina buffer memory in the system control section 93 (described below) on alogical block-by-logical block basis.

The AV decoder 85 processes the digital data, which is an input VOB, ina prescribed manner to convert the data into a video signal or an audiosignal. Specifically, the AV decoder 85 includes a system decoder 86, avideo decoder 87 and an audio decoder 88.

The system decoder 86 receives the digital data stream transferred fromthe buffer memory on a logical block-by-logical block basis (i.e., on apacket-by-packet basis) and distinguishes a stream ID and a sub streamID in the header of each packet, thereby classifying the data into amoving picture data pack, an audio data pack and a managementinformation pack. At this point, the moving picture data pack is outputto the video decoder 87. Regarding the audio data pack, only the audiodata pack having a designated stream number is output to the audiodecoder 88 in accordance with a decode stream instruction command sentfrom the system control section 93. The management information pack isoutput to the system control section 93. The moving picture data packinput to the video decoder 87 is extended by the prescribed formatdefined by the MPEG2 format and output as digital video data. Then, thedigital video data is converted into a video signal of the NTSC formatand externally output. The audio data input to the audio decoder 88 isdecoded in the LPCM or AC3 format in accordance with the data type, D/Aconverted, and then externally output as an audio signal.

The audio decoder 88 processes the digital data, which is an input AOB,in a prescribed manner in accordance with the data type, converts thedata into an audio signal, and externally outputs the data.

The system control section 93 includes a working memory and a CPUintegrated together and performs overall control of the DVD player.

The reproduction apparatus according to the present invention operatesin, for example, the following manner.

When a DVD is loaded on the DVD player, the system control section 93detects that the DVD is loaded from the optical sensor or the like.Then, the system control section 93 controls the mechanism controlsection 83 and the signal processing section 84, thereby controllingrotation of the DVD so as to cause the optical pickup 82 to seek to thelead-in region. Thus, the DVD player is initialized and reproductionstarts.

For starting the reproduction, the system control section 93 determineswhether or not the DVD player is in a video-oriented reproduction mode,by a reproduction mode determination section. When it is determined thatthe DVD player is in the video-oriented reproduction mode, the systemcontrol section 93 reads the video manager based on the informationwhich is read from the volume file management region. The system controlsection 93 refers to the PGC management information table for the videomanager menu to calculate the recording address of the PGC for thevolume menu. The resultant PGC is reproduced and retained inside. Whenthe PGC for the volume menu is retained inside, the system controlsection 93 refers to the retained PGC information to calculate the videoobject (VOB) to be reproduced and the recording address of the VOB onthe optical disk. When the VOB to be reproduced is determined, thesystem control section 93 outputs a control signal to the mechanismcontrol section 83 and the signal processing section 84 so as toretrieve the determined VOB from the DVD for reproduction. Thus, thevideo menu from which the user can select the title to be reproduced isdisplayed.

The user sees the menu and selects and defines the title that he/she isinterested in by designating the item number in the menu using theremote controller. Then, the system control section 93 receives thedesignation of the item number in the menu from the remote controllerand refers to the management information pack included in the VOB of thevideo menu which is being reproduced, the VOB being input from the AVdecoder 85, to execute a control command corresponding to the designatednumber. The control command is PlayTitle #n or the like, and the titlenumber to be reproduced is designated by “n”. As an execution operationby the PlayTitle command, the system control section 93 refers to thetitle search pointer table, which is a part of the audio manager, todetermine the audio title set (ATS) to which the designated titlebelongs to and the title number in the ATS. When the ATS is determined,the system control section 93 outputs a control signal to the mechanismcontrol section 83 and the signal processing section 84 so as toreproduce the ATS management information of the confirmed title set andretrieves the title search pointer table of the ATS which is a part ofthe ATS management information to the system control section 93. Whenthe title search pointer table is retrieved, the system control section93 refers to the table to determine the PGC information for starting thereproduction of the title to be reproduced. When the PGC information isdetermined, the system control section 93 outputs a control signal tothe mechanism control section 83 and the signal processing section 84 soas to reproduce the determined PGC information and retain theinformation in the inside buffer memory for the PGC information. Whenthe PGC information is retained, the system control section 93 refers tothe retained PGC information to determine the audio object (AOB) to bereproduced and the recording address thereof. Then, the AOB isreproduced by a control signal output to the mechanism control section83 and the signal processing section 84 from the system control section93.

The system control section 93 sequentially determines the AOBs to bereproduced and controls the reproduction thereof in accordance with theretained PGC information. When the reproduction of the final AOBindicated by the PGC information is completed, the system controlsection 93 searches for the PGC information of the next title andreproduces the AOBs described in the PGC information in the same manner.Thus, the all the titles are reproduced and the operation is stopped. Inaccordance with specific setting of the DVD player or the DVD, only onetitle can be reproduced before the operation is stopped, or a menu canbe displayed after reproduction of one or more titles is completed.

Next, a method for reproducing a still picture cell, a silent cell andan audio cell will be described in detail.

FIG. 19 shows a conventional method for reproducing the audio cell.Conventionally, for reproducing an MPEG2 stream, the leading end of theaudio cell pack 14 is first sought to and data reading starts. However,audio output does not immediately start but starts after an idle timeperiod, which is predetermined in each reproduction apparatus. The idletime period includes a time period required for determining the PTS ofthe audio data, a time period required for determining that data iscorrect, and a time period required for the muting circuit in an analogoutput section is to be transitioned from a mute state to a non-mutestate. Thus, the idle time period varies in accordance with the type ofreproduction apparatus. Especially when the reproduction section and thedecoder are accommodated in separate chassis, the idle time period tendsto be extended because determination on the PTS and the determination onthe correctness of the audio data are separately performed.

FIGS. 17A and 17B show a method for reproducing only audio data withoutdisplaying a still picture even though the still picture is included.FIG. 17A shows the method in the case where the reproduction isperformed from the leading end of the data, and FIG. 17B shows themethod in the case where the reproduction is performed in continuationfrom the previous cell.

In the case where reproduction is performed from the leading end of thedata by selecting a title or program from the menu or the like throughjumping, the leading pack of the silent cell is jumped to with referenceto the start address of the cell information. At this point, the STC,which is the reference time of the decoder is set with the SCR of theleading pack of the silent cell. Next, skipping and jumping of datacorresponding to a prescribed idle time period are performed withreference to the PTS of the silent cell, and the silent cell for theidle time period is reproduced. Audio output is prepared for during thisperiod. At this point, the next title number is not displayed on thedisplay device of the reproduction apparatus, and the passage ofreproduction time period is not updated. When the first PTS of the audiocell is detected, audio output is started simultaneously. In the casewhere the audio output is started and display of the title number andthe updating of the passage of the reproduction time period areperformed simultaneously when the first PTS of the leading cell isdetected, the reproduction apparatus behaves as if the audio data isoutput simultaneously with the completion of the jump such as menuselection. In the case where the reproduction is performed incontinuation from the previous cell, a still picture pack is jumped overand a silent cell is jumped over or skipped except for the idle timeperiod. At this point, by continuously counting the STC, which isreference for the system time, the interval between the completion ofthe audio output by the previous cell and the start of the audio outputby the next cell equals the audio pause time period. The counting of theSTC is continued when the physical allocation information and the timeattribute information both have a value indicating “continue”. Wheneither one of them indicates “no-continue”, the same processing as inthe jump from the menu is performed, and thus the STC is reset at theleading end of the silent cell pack. Even in the case where there is nostill picture cell, the method is substantially the same as describedabove. In the case where there is no silent cell and the reproductionstarts from the leading end of the data, the operation is similar to theconventional operation shown in FIG. 19. In the case where thereproduction is performed in continuation from the previous cell, theoperation is as follows. When the time attribute information indicates“continue”, the audio cell is decoded as it is continuously from theprevious cell and audio data is output. When the time attributeinformation indicates “no-continue”, the operation is the same as theconventional operation shown in FIG. 19 as in the case where thereproduction is performed from the leading end of the data.

FIGS. 18A and 18B show a method for producing the audio data whiledisplaying a still picture. FIG. 18A shows the method in the case wherethe reproduction is performed from the leading end of the data, and FIG.18B shows the method in the case where the reproduction is performed incontinuation from the previous cell.

In the case where the reproduction is performed from the leading end ofthe data or by selecting a title or program from the menu or the likethrough jumping, the pack of the still picture cell is sought to fromthe cell information. Thus, the still picture cell is read and decoded.At this point, the STC, which is the reference time of the decoder, isset with the SCR of the leading pack of the still picture cell. Next,the leading pack of the silent cell is read. When an STC reaches an STCof the still picture cell, the still picture is displayed. The rest ofthe operation is the same as the operation when there is no stillpicture. The display of the still picture can be during the processingof the silent cell, simultaneously with the start of output of the audiocell, or after the start of output of the audio cell in the rangepermitted by the MPEG2 format. In the case where the reproduction isperformed in continuation from the previous cell, the still picture cellis read and decoded when a still picture pack is detected. Next, thesilent cell is processed. Whether or not the STC is set depends on thetime attribute information as in the case where there is no stillpicture cell. The rest of the operation is the same as the operationwhen no still picture is displayed, except that the still picture isdisplayed when the STC becomes a PTS of the still picture cell and thatthe STC is set with the SCR of the leading pack of the still picturecell.

FIGS. 20 through 23 are flowcharts each illustrating a program. In thecase where the physical allocation information of the programinformation shows “continue” and the program previously reproduced has aprogram number which is smaller by one than the program number of theprogram to be reproduced now, seek to the reading head for the DVD isnot specifically necessary. When the time attribute informationindicates “continue” and the reproduction is performed in continuationfrom the previous program, the STC, which is reference time for thedecoder, does not need to be reset.

The determination of whether or not the cell is a still picture cell canbe performed using the cell type in the cell information or using astill picture flag of the program information. The determination ofwhether or not the cell is a silent cell is performed by the cell typein the cell information. The determination that the cell is the finalcell is performed by comparing the termination address of the cellinformation and the address read from the data in the DVD. Thecompletion of the reproduction of the program can be determined by thecell index of the cell information returning to zero, the cell typeindicating a still picture cell or a silent cell, or the start cellnumber of the next program in the program information.

The skipping of the silent cell is performed while detecting the PTSwhen the silent cell is decoded or by obtaining the number of packs tobe skipped based on the data rate.

As described above, in the second example according to the presentinvention, program reproduction information including the start time andreproduction time period of each of audio data based on the reproductionstart time of the leading audio data in an MPEG2 stream is recorded inthe management region as a part of the reproduction control information.Accordingly, a multimedia information storing medium which realizesreproduction of high quality digital audio data and video data addedthereto under a restricted bit rate can be provided. The intervalbetween the reproduced audio data can be uniform even in low-costreproduction apparatuses or reproduction apparatuses having noreproduction function of video data. Thus, the title creators canprepare data easily.

According to the present invention, the wait time (start-up period)before the start of reproduction of an audio stream can be substantiallyuniform among a plurality of reproduction apparatuses having differentlevels of performance such as data processing speed.

Various other modifications will be apparent to and can be readily madeby those skilled in the art without departing from the scope and spiritof this invention. Accordingly, it is not intended that the scope of theclaims appended hereto be limited to the description as set forthherein, but rather that the claims be broadly construed.

What is claimed is:
 1. A recording medium comprising: an audio zoneregion for storing at least one audio object and audio title setinformation for managing the reproduction of the at least one audioobject, wherein each of the at least one audio object includes aplurality of cells, each of the cells containing audio information inthe form of an encoded audio stream, the audio title set informationcontains a plurality of sets of reproduction path information eachindicating the order of reproducing the at least one audio object, theplurality of cells include a silent cell and an audio cell following thesilent cell, the silent cell having audio information a variable amountof which is reproduced during a silent period, the audio cell havingaudio information to be reproduced after the silent period, the audioinformation included in the silent cell and the audio informationincluded in the audio cell have been encoded in accordance with the sameencoding type which is selected from a plurality of encoding types; andwherein each of the plurality of sets of reproduction path informationincludes reproduction order information indicating a reproduction orderfor reproducing the cells, location information indicating the locationof each of the plurality of cells on the recording medium, and typeinformation indicating the type of each of the plurality of cells, saidtypes including a silent cell type and an audio cell type.
 2. Arecording medium according to claim 1, wherein the amount of audioinformation reproduced from the silent cell varies as a function of astart-up period of an apparatus used to reproduce the at least one audioobject from the recording medium.
 3. A recording medium according toclaim 2, wherein a wait time comprising the start-up period of theapparatus and the duration of the audio information reproduced from thesilent cell is substantially the same for a plurality of differentapparatuses having different start-up periods.
 4. A recording mediumaccording to claim 1, wherein an output level of the audio informationincluded in the silent cell is substantially zero.
 5. A recording mediumaccording to claim 1, wherein the silent cell includes a first timestamp and a final time stamp, and the amount of audio informationreproduced from the silent cell varies as a function of a comparison ofa difference between the first time stamp and the final time stamp and astart-up period of an apparatus used to reproduce the at least one audioobject from the recording medium.
 6. A recording method for recordinginformation in a recording medium including an audio zone region,comprising the steps of: storing at least one audio object and audiotitle set information for managing the reproduction of the at least oneaudio object in the audio zone region of the recording medium, whereineach of the at least one audio object includes a plurality of cells,each of the cells containing audio information in the form of an encodedaudio stream, the audio title set information contains a plurality ofsets of reproduction path information each indicating the order ofreproducing the at least one audio object, the plurality of cellsinclude a silent cell and an audio cell following the silent cell, thesilent cell having audio information a variable amount of which isreproduced during a silent period, the audio cell having audioinformation to be reproduced after the silent period, the audioinformation included in the silent cell and the audio informationincluded in the audio cell have been encoded in accordance with the sameencoding type which is selected from a plurality of encoding types; andwherein each of the plurality of sets of reproduction path informationincludes reproduction order information indicating a reproduction orderfor reproducing the cells, location information indicating the locationof each of the plurality of cells on the recording medium, and typeinformation indicating the type of each of the plurality of cells, saidtypes including a silent cell type and an audio cell type.
 7. Arecording method according to claim 6, wherein the amount of audioinformation reproduced from the silent cell varies as a function of astart-up period of an apparatus used to reproduce the at least one audioobject from the recording medium.
 8. A recording method according toclaim 7, wherein a wait time comprising the start-up period of theapparatus and the duration of the audio information reproduced from thesilent cell is substantially the same for a plurality of differentapparatuses having different start-up periods.
 9. A recording methodaccording to claim 6, wherein an output level of the audio informationincluded in the silent cell is substantially zero.
 10. A recordingmethod according to claim 6, wherein the silent cell includes a firsttime stamp and a final time stamp, and the amount of audio informationreproduced from the silent cell varies as a function of a comparison ofa difference between the first time stamp and the final time stamp and astart-up period of an apparatus used to reproduce the at least one audioobject from the recording medium.